Application Of Sodium Lauryl Sulfate Research Articles

Acute skin barrier disruption alters the secretion of lamellar bodies via the multilayered expression of ABCA12

BackgroundThe skin barrier consists of multiple lipid-enriched layers, which are characterized by lamellar repeated structures within the intercellular space. Sodium lauryl sulfate is a well-known substance that can disrupt the skin barrier. The mechanisms underlying the barrier repair process, especially the influence of topical sodium lauryl sulfate treatment on lipid transport in the barrier recovery phase, remain unresolved. ObjectiveTo understand the process of reconstruction of the intercellular lipid layer of the skin after acute barrier disruption by sodium lauryl sulfate treatment in vivo. MethodsFemale hairless mice were treated with 3 % sodium lauryl sulfate. Transepidermal water loss measurement, histopathological analysis, and gene expression analysis were performed from 1 to 288 h after the topical application of sodium lauryl sulfate. Western blot analysis, immunofluorescence staining, and transmission electron microscopy analysis were performed to examine the expression level of ATP-binding cassette, sub-family A, member 12 (ABCA12), and the secretion level of lamellar bodies. ResultsWe observed rapid hyper-keratinization at the stratum corneum and the subsequent concurrent secretion of lamellar bodies into the intercellular space of the stratum corneum during the process of skin barrier recovery. ABCA12 expression associated with lipid transportation into lamellar bodies was transiently upregulated and observed in multiple layers in the upper epidermis, especially in the stratum granulosum. ConclusionThe skin reacts appropriately to maintain its barrier function by first initiating hyper-keratinization and then increasing lamellar body secretion. Activation of ABCA12 is an essential factor for the recovery of skin barrier function.

Characterization of cowhage-induced pruritus in inflamed and non-inflamed skin.

Pruritus is a major symptom of many inflammatory diseases and impacts greatly the quality of life in patients. We aimed to specify the characteristics of experimentally induced pruritus in normal skin and in experimentally induced inflammatory dermatitis in healthy volunteers. Skin inflammation was induced by the repeated application of sodium lauryl sulphate (SLS 2%) on the volar forearms of 30 healthy volunteers. Inflammatory dermatitis intensity was assessed using the eczema score adapted from Frosch and Kligman. Non-histaminergic pruritus was induced by cowhage spicules rubbed on the volar forearms and recorded for 30min on a 10-cm visual analogue scale (VAS) in both non-inflamed and inflamed skin. Induction of inflammatory dermatitis by SLS resulted in a mild inflammatory dermatitis with an inflammation score of 2.3±0.1 within 7days of treatment. Cowhage-induced pruritus was of markedly higher intensity (P<0.001), and all but two individuals had higher maximum pruritus intensity in inflamed skin as compared to non-inflamed skin, whereas the kinetics of the pruritus response were similar. The quality of cowhage-induced pruritus was significantly different with more 'burning' and 'painful sensations' in inflamed skin (P<0.01). Maximum pruritus intensity in inflamed skin strongly correlated with maximum pruritus intensity in non-inflamed skin (r=0.51, P=0.004). Skin hydration, skin barrier integrity and dermatitis severity did not correlate with pruritus intensity. Taken together, pruritus in inflamed skin is perceived as more intense, painful and burning. This may explain, in part, why pruritus is a major driver of quality-of-life impairment in patients with chronic inflammatory skin conditions such as atopic dermatitis.

512 Impairment of skin microbiota by overcleansing

Our skin is daily aggressed by environmental factors and by certain personal care products (cleansers, deodorants, etc).Our obsession with cleanliness may do more harm than good for the balance of our skin’s microbiota and skin health. It has been observed that overcleanliness leads to an impairment of the skin barrier function and of skin microbiome balance leading to increased sensitivity, irritation and dryness. We explored the effect of a common surfactant found in hygiene products, on the physical skin and microbiotic barrier in vivo. At first, we applied SLS (Sodium Lauryl Sulfate, 0.5% occlusive patch for 24h) and we explored its effect on the skin microbiota using metagenomic sequencing (16S rDNA) before and 1 day after SLS application. Secondly, we explored skin microbiota and skin barrier function evolution over 7 days after a 1% SLS challenge in the presence of a formula containing purified rapeseed phytosterols and one containing its vehicle. Skin barrier function was assessed before, after SLS and 7 days after applying phytosterols and vehicle by measuring TEWL. Finally, skin microbiota recovery after a 0.5% SLS patch in presence of the same formula containing phytosterols was assessed at the same timepoint; (16S metasequencing). We confirmed that the surfactant impaired skin barrier function and evidenced that it decreased the commensal bacteria while increasing the opportunistic pathogenic bacteria. At the phylum level actinobacteria were decreased by 14% and at the family level, corynebacteriaceae, micrococcaceae and propionibacteriacea were decreased (-42%, -34%, -11%). At the genus level corynebacterium, micrococcus, paracoccus and propionibacterium were decreased (-42%, -39%, -36%, -11%), whereas pseudomonas and pantoea were increased (x2, x117). Interesting results were also obtained on staphylococcus (+38%), but a more resolutive technic is necessary to discriminate between strains. To counterbalance these SLS induced-modifications, we evidenced that purified phytosterols provide benefits to restore skin barrier and microbial skin flora.

Long-Term Monitoring of Skin Recovery by Micromachined Microwave Near-Field Probe

The water content in the epidermis correlates with different pathologic states of the skin; thus its assessment can aid the diagnosis and monitoring of conditions such as inflammation, edema, burns, and skin cancer. A micromachined microwave near-field probe, operating from 90 to 106 GHz, which, in contrast to earlier used microwave probes, has a minimized sensing area of $0.6\,\,\text {mm} \times 0.5$ mm and an optimized sensing depth of 400 $\mu \text{m}$ in tissue, has been developed and technically characterized by the authors earlier. This letter reports on the long-term monitoring of sodium lauryl sulfate (SLS)-induced skin irritations with the micromachined microwave probe. Aqueous solutions with 1%, 2%, 5%, and 10% SLS were applied to the forearm of a volunteer for 24 h and microwave reflection measurements were taken before and during 11 days after the SLS application. For all SLS-treated spots the microwave absorption reached the highest levels of 4 to 7 days after SLS application and afterward converged toward baseline levels again. The observed biphasic progression of the microwave reflection signal agrees well with trends from the literature for capacitance measurements and for epidermal thickness and signal attenuation in optical coherence tomography after SLS exposure. The measurements indicate that the microwave probe is very suitable to determine changes in the water content in the epidermis and can aid in the diagnosis of pathologic conditions including skin cancer.

Sodium Lauryl Sulfate Stimulates the Generation of Reactive Oxygen Species through Interactions with Cell Membranes.

Sodium lauryl sulfate (SLS), a representative anionic surfactant, is well-known to induce rough skin following single or multiple topical applications. The mechanism by which SLS induces rough skin is thought to result from the disruption of skin moisture function consisting of NMF and epidermal lipids. However, a recent study demonstrated that topically applied SLS easily penetrates into the living cell layers of the epidermis, which suggests that physiological alterations of keratinocytes might cause the SLS-induced rough skin. This study was conducted to clarify the effects of SLS on keratinocytes to demonstrate the contribution of SLS to the induction of rough skin. In addition, the potentials of other widely used anionic surfactants to induce rough skin were evaluated. HaCaT keratinocytes treated with SLS had increased levels of intracellular ROS and IL-1α secretion. Application of SLS on the surface of a reconstructed epidermal equivalent also showed the increased generation of ROS. Further, SLS-treated cells showed an increase of intracellular calpain activity associated with the increase of intracellular Ca2+ concentration. The increase of intracellular ROS was abolished by the addition of BAPTA-AM, a specific chelator of Ca2+. In addition, IL-1α also stimulated ROS generation by HaCaT keratinocytes. An ESR spin-labeling study demonstrated that SLS increased the fluidity of membranes of liposomes and cells. Together, those results indicate that SLS initially interacts with cell membranes, which results in the elevation of intracellular Ca2+ influx. Ca2+ stimulates the secretion of IL-1α due to the activation of calpain, and also increases ROS generation. IL-1α also stimulates ROS generation by HaCaT keratinocytes. We conclude from these results that the elevation of intracellular ROS levels is one of the causes of SLS-induced rough skin. Finally, among the other anionic surfactants tested, sodium lauryl phosphate has less potential to induce rough skin because of its lower generation of ROS.

Skin reaction and regeneration after single sodium lauryl sulfate exposure stratified by filaggrin genotype and atopic dermatitis phenotype.

Filaggrin is key for the integrity of the stratum corneum. Mutations in the filaggrin gene (FLGnull) play a prominent role in atopic dermatitis (AD) pathogenesis. People with AD have increased susceptibility to irritants. However, little is known about the effect of filaggrin genotype and AD phenotype on irritant response and skin regeneration. To investigate the role of FLGnull and AD groups for skin reaction and recovery after sodium lauryl sulfate (SLS) irritation. This is a case-control study comprising 67 subjects, including healthy controls and patients with and without FLGnull and AD. Reactivity to different doses of SLS at 24, 48, 72 and 145h after SLS application was measured by transepidermal water loss (TEWL) and laser Doppler flowmetry (LDF). Reactivity was assessed univariately and by pattern analysis. All patient groups showed a higher degree of skin-barrier disruption and inflammation than did controls in response to SLS. Assessing reactivity by the delta value of the area under the curve for both TEWL and LDF showed significant differences between healthy controls and those with the AD phenotype, irrespective of filaggrin mutation. The poorest regeneration was among those with the AD phenotype. The two AD phenotype groups were separated by multivariate technique, due to earlier inflammatory reactivity among subjects with FLGnullplus AD compared with the AD phenotype alone. Both skin reaction and regeneration were significantly different between the patient population and the healthy controls. Additionally, response severity and regeneration depended more on AD phenotype than on filaggrin genotype, whereas the response was more rapid among the FLGnullplus AD individuals.

Tranexamic acid accelerates skin barrier recovery and upregulates occludin in damaged skin

Tranexamic acid (TA) is a traditional plasmin inhibitor, and its role in the renovation of damaged skin has become the topic of a lot of research. The aim of this study is to determine whether TA could repair the skin barrier by means of tight intercellular junctions. Two kinds of damaged skin models were set up and subjected to repeated application of sodium lauryl sulfate and irradiation of ultraviolet B. Through bioengineering technology and immunohistochemistry tests, TA-induced changes in skin were detected. After 1, 3, 7, and 14days of application, TA can significantly accelerate barrier recovery and decrease the melanin index values of ultraviolet B irritation skin. The mean optic density of occludin from TA treatment is higher than from self-repair. These experiments suggest that TA can accelerate skin barrier recovery and upregulate occludin induced by physicochemical damages of human skin, but it is advisable to perform more research on the upregulation of occludin in molecular mechanism in the future.

A novel model of inflammatory pain in human skin involving topical application of sodium lauryl sulfate

Sodium lauryl sulfate (SLS) is a known irritant. It releases pro-inflammatory mediators considered pivotal in inflammatory pain. The sensory effects of SLS in the skin remain largely unexplored. In this study, SLS was evaluated for its effect on skin sensory functions. Eight healthy subjects were recruited for this study. Skin sites were randomized to topical SLS 0.25, 0.5, 1, 2% and vehicle for 24 h. Topical capsaicin 1% was applied for 30 min at 24 h after SLS application. Assessments included laser Doppler imaging of local vasodilation and flare reactions, rating of spontaneous pain, assessment of primary thermal and tactile hyperalgesia, and determination of secondary dynamic and static hyperalgesia. SLS induced significant and dose-dependent local inflammation and primary hyperalgesia to tactile and thermal stimulation at 24 h after application, with SLS 2% treatment eliciting results comparable to those observed following treatment with capsaicin 1%. SLS induced no spontaneous pain, small areas of flare, and minimal secondary hyperalgesia. The primary hyperalgesia vanished within 2-3 days, whereas the skin inflammation persisted and was only partly normalized by Day 6. SLS induces profound perturbations of skin sensory functions lasting 2-3 days. SLS-induced inflammation may be a useful model for studying the mechanisms of inflammatory pain.

Measuring transepidermal water loss: a comparative in vivo study of condenser‐chamber, unventilated‐chamber and open‐chamber systems

Two main systems have been utilized for measuring transepidermal water loss (TEWL): open chamber and closed chamber. Yet, further validation and standardization studies may be necessary to reveal the sensitivity, precision, and robustness of these instruments. Three instruments are compared for their applicability to assess TEWL: unventilated chamber, open chamber and condenser chamber. The comparative study was performed on human forearm skin (n=6), in the normal condition (baseline), and after (1) 10 tape strippings on both arms, (2) moisturizer cream (Eucerin) and petrolatum application for 1 h, and (3) 1% sodium lauryl sulfate (SLS) aqueous solution and distilled water (as control) application for 20 min. The condenser-chamber system, was the only device among these three that could show the effect of tape stripping on TEWL values as compared with baseline (P<0.001). The effect of moisturization, in terms of % change of TEWL values after application of cream and petrolatum, did not show significant difference between devices (P>0.05). However, only the values obtained from condenser-chamber device revealed a highly significant change as compared with baseline (P<0.001). Condenser-chamber system could also discriminate between the effect of moisturizer and petrolatum on TEWL values (P<0.05). The change of TEWL values after SLS application was shown to be significant by unventilated and condenser-chamber systems (P<0.05). However, none of the devices differentiated between the effect of water and 1% SLS solution applied for 20 min. The values obtained from all three instruments correlate well with each other (P<0.001). Our results highlight the differences between two closed-chamber TEWL measurement instruments, which are designed based on different measurement principles. This may provide insights to find the best practice to improve the quality, precision and sensitivity of the measurements.

Effects of disinfectants and detergents on skin irritation

We investigated the biological response of regular human skin to alcohol-based disinfectants and detergents in a repetitive test design. Using non-invasive diagnostic tools such as transepidermal water loss, laser-Doppler flowmetry and corneometry, we quantified the irritative effects of a propanol-based hand disinfectant (Sterillium), its propanol mixture (2-propanol 45% w/w and 1-propanol 30% w/w), sodium lauryl sulfate (SLS) 0.5% and distilled water. The substances were applied in a 2-D patch test in a repetitive occlusive test design to the back. Additionally, we performed a wash test on the forearms that was supposed to mimic the skin affection in the normal daily routine of health care workers. In this controlled half-side test design, we included the single application of the hand rub, SLS 0.5% and water as well as a tandem application of the same substances. Patch test and wash test showed similar results. The alcohol-based test preparations showed minimal irritation rather comparable to the application of water. However, the detergent SLS produced stronger barrier disruption, erythema and dryness than the alcohol-based preparations. There was no additional irritation at the combined use of SLS and disinfectants. By contrary, there was even a decrease in barrier disruption and erythema induced by the tandem application of SLS followed by alcohol-based disinfection compared with the use of SLS alone. These findings show a less irritant effect of alcohol-based disinfectants on the skin than detergents. Our study shows that there is no summation of irritating effects of a common detergent and propanol and that the combination of washing and disinfection has a rather protective aspect compared with washing alone.

Wirkung von Linola®-Emulsion im Vergleich zu einer Hydrokortison-Emulsion im Testmodell einer irritativen Kontaktdermatitis

Kortikosteroid-haltige Externa und lipidhaltige Emollientien sind die wichtigsten Ekzemtherapeutika. Externa mit ungesättigten Fettsäuren, insbesondere Linolsäure, werden seit Jahren erfolgreich zur Ekzembehandlung und Nachbehandlung eingesetzt. Ziel der Studie war es, die hautregenerierende Wirkung einer ungesättigte Fettsäuren enthaltenden Emulsion (Linola®) im Vergleich zu einer 0,25 %-Hydrokortison-haltigen (Ebenol®) Emulsion im Modell der irritativen Kontaktdermatitis zu untersuchen. Bei 30 Probanden wurde eine irritativ-toxische Kontaktdermatitis durch Applikation von Natriumlaurylsulfat unter einer okklusiven Patch-Testkammer induziert. Anschließend erfolgte die offene Applikation der beiden Prüfpräparate zweimal täglich über neun Tage. Beide Produkte führten zu einer signifikanten Erhöhung der durch Irritation verringerten Stratum corneum-Hydratation. Der durch die Irritation erhöhte TEWL wurde durch Behandlung mit beiden Präparaten verringert. Überraschenderweise reduzierte Linola®-Emulsion die Hautrötung als Marker der Entzündung nach 3 Tagen im gleichen Ausmaß wie die 0,25 %-Hydrokortison-haltige Emulsion. Zusammengefasst zeigte eine Emulsion mit ungesättigten Fettsäuren, insbesondere Linolsäure, im Modell der irritativen Kontaktdermatitis eine gleich gute regenerative und antientzündliche Wirkung wie eine 0,25 %-Hydrokortison-haltige Emulsion.

How irritant is alcohol?

Alcohol-based hand rubs are used worldwide to prevent transmission of nosocomial pathogens. To investigate skin irritation caused by alcohols alone and in combination with detergent washing. Single and repetitive patch testing with 60-100% alcohols [ethanol, 1-propanol, 2-propanol (synonyms: isopropyl alcohol, isopropanol)], a positive control [0.5% sodium lauryl sulphate (SLS)] and negative controls (empty chamber and water) were performed. Wash tests were performed with 80% ethanol and 0.5% SLS on the forearms with each agent alone and with both agents in a tandem design. Skin hydration, erythema and barrier disruption [measured as transepidermal water loss (TEWL)] were evaluated (always 15 volunteers). We found no significant change in skin barrier or erythema induced by the alcohols in the patch tests, whereas skin hydration decreased significantly. Application of alcohols to previously irritated skin did not show a stronger skin barrier disruption than application of SLS alone. Wash tests demonstrated that alcohol application caused significantly less skin irritation than washing with a detergent (TEWL, P < 0.001; skin hydration, P < 0.05; erythema, P < 0.05). Even on previously irritated skin, ethanol did not enhance irritation. By contrast, a protective effect of ethanol used after skin washing was observed (TEWL, P < 0.05; skin hydration, P < 0.05; erythema, P < 0.05). Alcohol-based hand rubs cause less skin irritation than hand washing and are therefore preferred for hand hygiene from the dermatological point of view. An alcohol-based hand rub may even decrease rather than increase skin irritation after a hand wash due to a mechanical partial elimination of the detergent.

Use of the Reviscometer® for measuring cosmetics‐induced skin surface effects

The Reviscometer RVM600 that measures resonance running time (RRT) has been shown to be inversely related to the skin stiffness. However, very few publications describe the use of this instrument for testing the effect of cosmetic products. Slight xerotic skin condition was induced by using an alkaline soap for 1 week. Skin has then been rehydrated with a lotion or further dehydrated and dried with sodium lauryl sulfate (SLS). Skin condition at the different stages of the study was evaluated by visual assessment for dryness and redness and by non-invasive methods (Corneometer, Cutometer, Reviscometer, Evaporimeter and squamometry). All methods showed highly significant changes after the slight drying phase with the soap usage. They illustrated skin repair after lotion treatment and further skin impairment after SLS application. Nevertheless, the Reviscometer was able to better statistically discriminate between the treatments (water, lotion, SLS) than the Cutometer . Measurement of the RRT along the transversal axis of the forearms was the most sensitive for differentiating between normal and dry skin and between the treatments on the basis of skin mechanical properties. The Reviscometer RVM600 is a sensitive instrument able to detect slight skin surface effect of cosmetics. Combined with published literature on the interpretation of RRT measurements on polymeric gel or in different skin conditions (elderly skin and photoaged skin), the Reviscometer looks to be a recommendable instrument to measure slight changes in SC stiffness/suppleness induced by cosmetic products.

The nature of ultrasound–SLS synergism during enhanced transdermal transport

Ultrasound and sodium lauryl sulfate (SLS) exhibit a synergistic effect on transdermal transport, when applied simultaneously on the skin. The synergistic mechanism is not fully understood. Previous studies have shown that application of ultrasound simultaneously with SLS, results in enhanced mass transfer and improved penetration and dispersion of the surfactant. In this study we demonstrate that simultaneous application of ultrasound and SLS leads to modification of the pH profile of the stratum corneum. This pH modification within the stratum corneum's microenvironment, can affect both the structure of the lipid layers and the activity of SLS as a chemical enhancer due to its improved lipophilic solubility. The altered pH profile that results in improved SLS lipophilic solubility, together with improved SLS penetration and dispersion, can explain the synergistic enhancing effect of ultrasound and SLS on transdermal transport.

Induction of a Hardening Phenomenon by Repeated Application of SLS: Analysis of Lipid Changes in the Stratum Corneum

Adaptation of the skin to repeated influence of exogenous irritants is called the hardening phenomenon. We investigated the stratum corneum lipid composition before and after induction of a hardening phenomenon. Irritant contact dermatitis was induced in 23 non-atopic volunteers by repeated occlusive application of 0.5% sodium lauryl sulfate (SLS) over 3 weeks. At 3, 6 and 9 weeks after irritation, the SLS responses of pre-irritated skin and normal skin were compared. The horny layer lipid composition (ceramides 1-7, cholesterol and free fatty acids) was assessed before irritation and 3, 6 and 9 weeks after irritation. During the first 2 weeks of irritation the transepidermal water loss increased continuously and seemed to decrease during the third week (effect of adaptation). The barrier function of pre-irritated sites was more stable to SLS challenge. Three weeks after irritation, there was a significant increase of ceramide 1 (p<0.001). The only volunteer without hardening phenomenon showed no increase of ceramide 1. Ceramide 1 seems to play a key role as a protection mechanism against repeated irritation.

Simultaneous sodium lauryl sulphate testing improves the diagnostic validity of allergic patch tests. Results from a prospective multicentre study of the German Contact Dermatitis Research Group (Deutsche Kontaktallergie-Gruppe, DKG)

There is evidence that a higher skin susceptibility may induce nonspecific erythematous or weak positive reactions to contact allergens in patch testing. To evaluate whether simultaneous application of sodium lauryl sulphate (SLS) along with diagnostic patch tests with contact allergens can provide information regarding skin irritability which may help to discriminate allergic from nonspecific irritant reactions to contact allergens. Between July 2001 and June 2003, this prospective study collected patch test data of 5971 patients from 19 centres in Germany and Austria in the Information Network of Departments of Dermatology (IVDK). In addition to contact allergens (standard series and eight known 'problematic' allergens with a low reaction index and a high positivity ratio: 1,3-diphenylguanidine, amerchol L-101, benzalkonium chloride, benzoyl peroxide, cocamidopropyl betaine, octyl gallate, phenyl mercuric acetate and propylene glycol), patches with SLS 0.5% and 0.25% aq. were applied. Reactions to the allergens and to SLS were analysed at the IVDK data centre. The association between an erythematous or positive reaction to a certain allergen and an irritant reaction to SLS was assessed with logistic regression analysis, at the same time controlling for the influence of age and sex. Of the 29 allergens of the standard series, 23 and 21 gave a higher percentage of nonspecific erythematous reactions in patients with an irritant reaction to 0.25% and 0.5% SLS, respectively, in comparison with SLS-negative patients. All eight 'problematic' allergens gave an increased percentage of nonspecific erythematous reactions. Similarly, 22 and 21 allergens of the standard series gave a higher percentage of positive allergic reactions in patients with an irritant reaction to 0.25% and 0.5% SLS, respectively, and seven of the eight 'problematic' allergens gave a higher percentage of positive allergic reactions (exception: octyl gallate). For most allergens, the markers of skin reaction (reaction index and positivity ratio) were worse in SLS-positive patients. Differences were more pronounced when testing with SLS 0.25% than with SLS 0.5%. Because there is a convincing association between skin irritability (evaluated by SLS test) and the degree of skin reaction to contact allergens, the SLS test may help in deciding whether a doubtful erythematous or weakly 'positive' skin reaction should be interpreted as allergic or irritant.

Additive Impairment of the Barrier Function and Irritation by Biogenic Amines and Sodium Lauryl Sulphate: A Controlled in vivo Tandem Irritation Study

Biogenic amines are potential irritants e.g. in fish-, meat-, milk- and egg-processing professions like cooks, butchers and bakers. The aim of this study was to test the irritative and barrier-disrupting properties of the biogenic amines ammonium hydroxide (AM), dimethylamine (DMA) and trimethylamine (TMA). A repeated sequential irritation of 30 min twice per day was performed over a total of 4 days (tandem repeated irritation test) on the back of 20 healthy volunteers of both sexes with AM, DMA, TMA and sodium lauryl sulphate (SLS). The epidermal barrier function was assessed with a Tewameter TM 210, stratum corneum surface pH was measured with a Skin-pH-Meter 900, inflammation was assessed with a Chromameter CR-300 on the a* axis for redness and a visual score was recorded. All tested biogenic amines (AM, DMA and TMA) induced a barrier disruption and a pH increase paralleled with a 1-day-delayed onset of inflammatory signs. These effects were further enhanced and accelerated by a sequential application of SLS together with the biogenic amines, and inflammation occurred earlier than with the single compounds. Acetic acid (AA) in contrast did only show mild barrier disruption and no significant inflammatory signs. Our system allowed a ranking of the different compounds in their irritative potential in the tandem irritation with SLS: SLS > NaOH > TMA > AA > AM > DMA. The results are suggestive that in the food-processing industry the simultaneous contact with biogenic amines and harmful detergents like SLS should be minimized.

Fruit acids and sodium hydroxide in the food industry and their combined effect with sodium lauryl sulphate: controlled in vivo tandem irritation study

Cutaneous exposure to a variety of irritants has been extensively studied in recent years. Nevertheless, knowledge of the induction of irritant dermatitis, especially by mild irritants at low doses and for a short duration of exposure, is still incomplete. To quantify the irritant effects and barrier disruption properties of ascorbic acid (ASC), acetic acid (ACA) and sodium hydroxide (NaOH), particularly in combination with an anionic detergent, sodium lauryl sulphate (SLS). In a tandem repeated irritation test, the irritants were applied for 30 min twice daily for 4 days to the skin of the mid-back of 19 healthy volunteers of both sexes. We used bioengineering techniques for measurement of transepidermal water loss (TEWL) and skin colour reflectance, as well as visual scoring. Repeated application of ASC and ACA caused a moderate increase in TEWL and erythema. The sequential application of ASC or ACA and SLS enhanced these effects. NaOH induced a strong reaction when applied both occlusively and nonocclusively as well as in combination with SLS, with an early onset of the inflammatory signs, leading to discontinuation of the application on the third day in most of the test fields. Notably, the irritant effect of NaOH was not as marked when applied sequentially with SLS. Our results demonstrate that concurrent application of an anionic detergent and a mild acidic irritant can lead to disruption of the barrier function which, although not additive, is still considerable. The combined application of SLS and mild acids does not prevent SLS-induced irritation. Furthermore, we showed that NaOH in low concentrations may also act as a potent irritant but that its effect is not enhanced by SLS. The necessity of adequate skin protection and reduction of contact with substances that are potentially barrier disruptive and irritant, e.g. in the food industry, is emphasized, not only when handling detergents, but also when processing food products.

Influence of a detergent on skin response to methyldibromo glutaronitrile in sensitized individuals.

The present study was undertaken to evaluate the combined effect of the preservative methyldibromo glutaronitrile (MDBGN) and sodium lauryl sulfate (SLS) on the elicitation response of allergic contact dermatitis. 20 volunteers with contact allergy to MDBGN were patch tested with 5 concentrations (10, 50, 100, 500 and 1000 p.p.m.) of MDBGN alone and in combination with 0.25% SLS on the upper arms for 24 h. Skin reactions were evaluated by clinical scoring, and data were evaluated by logistic dose-response models. Additionally, evaluation of skin reactions was performed by measurement of transepidermal water loss (TEWL) and skin colour. Measurements were obtained at baseline and at D3 and D7. As evaluated by clinical assessment, allergic reactions to MDBGN were elicited at lower concentrations when applied in combination with SLS than when applied alone. The response was augmented by a factor of 6.4. An increased response to combined exposure to SLS and MDBGN as compared with MDBGN alone was confirmed by TEWL and colour measurements. Effects of exposure time and concentration of the detergent are discussed. In conclusion, an augmented response was found after concurrent application of MDBGN and SLS. The response was augmented by a factor of 6.4, with confidence limits of 2.8-14.6 (P < 0.0001). This result is important in relation to the determination of threshold values and the risk assessment of contact allergens in consumer and industrial products, where allergens are often present in combination with surfactants.

Tacrolimus enhances irritation in a 5-day human irritancy in vivo model.

Tacrolimus (FK 506) is a macrolide discovered in 1984 as a metabolic product of Streptomyces tsukabaensis. It has been used successfully in treating atopic dermatitis, allergic contact dermatitis, lichen planus mucosae and pyoderma gangrenosum. In the present study, we evaluated the anti-inflammatory activity of FK 506 in 2 human skin inflammation models. FK 506 as Protopic(R) cream was tested (i) in a 4-day repetitive irritation test with 2 x daily application of sodium lauryl sulphate (SLS), and (ii) in a UVB erythema model. The effect was evaluated visually and quantified by non-invasive bioengineering methods, namely chromametry and tewametry (TEWL). When FK 506 was applied 30 min after SLS irritation, an increased inflammation in comparison to controls was observed with all 3 methods, with only the TEWL data reaching statistical significance. 1 x daily application of FK 506 for 5 days, starting at the end of the 4-day irritation period, was without any effect. Similarly, no effect of FK 506 was seen in the UVB model. In conclusion, FK 506 was shown to enhance experimentally induced irritant contact dermatitis and not to accelerate healing of irritant contact dermatitis and UVB erythema.